HOW TO: USE ADJUVANTS

Which of these products is which and which of them do I use? Do I need to use them at all? Are they all different or is one the same as the other? The terminology is confusing, which means knowing when and how to use them is confusing. The broad term — adjuvants — is a category of products used to enhance the performance of pesticide applications. In general, they cause the pesticide to spread or stick or penetrate the plant material, with the result of more effective pest control. In order to understand how to use these products, you must first be able to differentiate between them.

Wetting agents or surfactants are one and the same. They reduce the surface tension of the pesticide, allowing it to spread more easily over the leaf. Most pesticides are diluted with water prior to spraying. Water molecules are chemically attracted to each other. This is why water droplets form — the water molecules are trying to get as close to each other as possible, and the result is a ball. This ball rolls right off the leaf when pesticide is applied. Surfactants, also known as wetting agents, reduce the chemical attraction, therefore allowing the pesticide droplet to spread out over the leaf, instead of rolling off.

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Surfactants are categorized as cationic, anionic or non-ionic. All of these refer to whether there is a positive charge, negative charge or no charge. Each pesticide label will specify which product to use. In general, non-ionic surfactants are often used with systemic pesticides and anionic surfactants are added to contact pesticides. Don't assume you know which one to use. Read the label.

Stickers increase the chemical attraction of the pesticide to the pest surface. They increase the length of time the pesticide stays in contact with the pest, resists being washed off by rain and reduces evaporation and volatilization.

There are also extenders, which work like stickers, and plant penetrants, which work like surfactants.

Some general guidelines for their use include:

  1. Read the label. Some manufacturers produce adjuvants that are most compatible with their products. If an adjuvant is needed, information on what and how much to use will be on the label.

  2. Some pesticides have adjuvants manufactured in them so no additional adjuvants are needed.

  3. Some pesticides recommend adjuvants for certain uses, but not others, for the same pesticide. Again, read the label entirely.

  4. You may have a colleague who recommends using a certain type of dish soap. Avoid using anything not recommended by the manufacturer. The dish soap may work on some plants, but may be phytotoxic to others. If the dish soap does not have the correct charge (anionic or non-ionic), you may chemically change the ability of the pesticide to control the target pest.

  5. Pay more attention to the pesticide label and choose the adjuvant that is recommended. Makers of the adjuvants want to sell lots of product as do other manufacturers. Their claims may not always match your purpose and your pesticide.

  6. An adjuvant may not be needed at all. Check the label and mix accordingly.

  7. There are many other products recommended for tank mixing such as defoaming agents, thickeners, drift retardants and pH modifiers. Be sure what your pesticide label is recommending and mix accordingly.

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